tropism
movement of an organism, or part of an organism, in response to an external source of stimulus, usually toward or away from it.
thigmotropism
directional growth movement which occurs as a mechanosensory reaction to touching it.
chemotropism
movement of an organism, or part of an organism, in response to an external chemical gradient, usually toward or away from it
phototropism
growth of an organism in response to a light stimulus
hydrotropism
growth or movement in a sessile organism toward or away from water, as of the roots of a plant